Unwrap the frozen cheesy garlic bread slices and separate them on a chopping board to defrost.
Fry the onion and beef in a large saucepan for 8 minutes until the beef is browned.
Stir in the flour followed by the tomatoes, tomato purée, wine, and boiled water.
Add the herbs, bay leaf, and stock cube, then season and simmer for 10 minutes until thickened.
Stir in the courgette and mushrooms and simmer for 5 minutes until heated through.
Preheat the grill to its highest setting.
Prewarm a 2.5 litre ovenproof dish with hot water, discard the water, and fill with the bolognese sauce.
Halve the garlic bread slices horizontally and arrange them on top of the sauce.
Grill the pie for 5 minutes until the bread is crisp and golden.